The Belfast–Derry railway line (referred to as the Derry~Londonderry Line by NI Railways[1]) runs from Belfast to Derry in Northern Ireland. This line is composed of mainly single track from just below Mossley West station up to Londonderry Waterside station with passing points at Antrim, Ballymena, Ballymoney, Coleraine and Castlerock.

On weekdays, stations between Great Victoria Street and Coleraine have an hourly service in both directions, with each outbound train alternating between a service to Londonderry Waterside, and a service to Portrush, except for some peak time trains which terminate at Coleraine. In the other direction, all trains run hourly to Great Victoria Street, with the exception of some late night and peak time services, which terminate at Belfast Central. Stations between Coleraine and Londonderry Waterside are served every two hours in each direction.

On Saturdays, the service remains much the same throughout the line as during the week, except for a reduction in peak-time services.

On Sundays, all trains run between Great Victoria Street and Londonderry Waterside, with the exception of the first and last services of the day, which start from or terminate at Coleraine. Only seven trains run each way on the Derry~Londonderry Line on Sundays.[2]

Any passengers travelling to Portrush on Derry-bound services, or to Londonderry on Portrush-bound services, have to change at Coleraine station.

Prior to 2001 and the reopening of the Bleach Green line, services operated via Crumlin, Glenavy, Ballinderry and Lisburn. The reopening of the Bleach Green line resulted in shorter journeys between Belfast and Londonderry. A skeleton service continued on the Lisburn-Antrim line until 2003, when the line and its stations were closed. This section of railway is now used solely for driver training, unless emergency diversions are required.

In August 2011 it was planned to reduce services on the Coleraine to Londonderry section to five services, in each direction on weekdays, to facilitate safety improvement works during 2012. A refurbishment of the line was due to commence in April 2012, however the £75 million that it was to cost, was unavailable. This resulted in opposition from supporters of the section who feared that the line would be permanently closed down.[3]

In October 2011, after years of uncertainty, DRD minister Danny Kennedy relocated funding from the A5 dualling project to the railway upgrade project, allowing for a 3 phase upgrade, which commenced in July 2012.

Phase 1 saw the line close for 9 months to completely relay two sections (Coleraine to Castlerock; and Eglinton to Londonderry) of the route, extending the life of the remaining section by converting the currently jointed track to continuous welded rail, elimination of wet spots, and essential bridge repairs. This was completed on 24 March 2013, and new timetable changes have resulted in a morning train reaching Derry before 9am for the first time since Northern Ireland Railways took control of the network in the 1960s.

Phase 2 was due to commence in 2014/15, but is currently delayed, consisting of the introduction of a passing loop as well as resignalling the route. It will see signal cabins in Castlerock and Londonderry close down, centralising the signalling in Coleraine, and deliver an hourly service between Derry and Belfast.[4]

Phase 3 will include the complete relay of track between Castlerock and Eglinton by 2021 delivering half hourly services.[5]

Other future plans for the Londonderry line include the reinstatement of the double line from Antrim to Ballymena, the doubling of the track from Monkstown to Templepatrick, and possible relocation of the route terminus in Londonderry.

Coleraine has a bascule bridge for the railway over the navigable River Bann.[6] Just after Castlerock station there are two tunnels created during an event known as the Great Blast in October 1845. Castlerock tunnel is 668 yards long and is the longest operational railway tunnel in Northern Ireland. After passing through a short opening trains pass through the shorter Downhill tunnel which is 301 yards in length.[7]

Signalling on the line from Great Victoria Street to Slaught level crossing (just south of Ballymena station) is controlled by the Belfast Central control terminal. From Ballymena, the signalling and level crossings are controlled by the Coleraine signal cabin. After trains depart Coleraine an Electric Train Staff system operates between Coleraine and Castlerock. This is when the driver obtains a token to access the portion of the line. Castlerock has its own signal cabin, which controls signalling from up to Ballykelly, where the driver hands the token to the signal controller and obtains another to allow the trains to proceed on to Londonderry. Londonderry also has a signal control terminal which controls signalling from Eglinton. Most of the Belfast to Londonderry line is controlled by colour light signals, but Castlerock station still boasts the semaphore signals of the somersault-type typical of NCC features.